Increasing traffic density and increased construction on free surfaces are continuously restricting traffic space, in particular in population centers. Available parking space is limited and the search for a suitable parking space is an additional burden on the driver besides the ever-increasing traffic. Therefore, semiautonomous parking assistance systems (SPA) have been developed that are intended to assist the driver in parking. This relieves the driver of the decision as to whether a given parking space is sufficient for a parking maneuver.
A number of different of parking assistance systems are known, including, for example, parking assistance systems having a “parking space measurement” function (PSM) using sensors mounted on the side of the vehicle to measure a parking space as the vehicle drives by. If the system detects a parking space large enough for the vehicle, this is signaled to the driver. In the subsequent parking maneuver, the system provides the driver with instructions or warning signals for parking.
German Published Patent Application No. 198 47 013 describes such a parking assistance system having a parking space measurement function in which an analyzer unit compares a distance signal output by a sensor device with a distance limit value and a warning signal transducer generates a warning signal that corresponds to the remaining routing distance. The remaining distance from an obstacle (e.g., a parked vehicle, edge of the curb or the like) may thus be signaled to the driver.
One problem with this parking assistance system, however, is the great inertia in outputting the warning signal under some circumstances. In other words, since the parking assistance system operates based on distance, it may happen that the driver receives a warning just before coming in contact with an obstacle. This is the case when parking is done at a relatively high speed in particular, because the stopping distance may be greater than the remaining distance from the obstacle.
This problem occurs to an increased extent with “semiautonomous parking assistance systems having steering intervention.” With such a system, the driver is relieved of the steering maneuver during the operation of parking the vehicle. The vehicle is steered automatically, so it automatically performs the steering intervention measures required for the parking maneuvers so that the driver need only accelerate and brake. However, experience has shown that such a facilitated parking maneuver results in the driver parking at a much higher speed because he is relying on a correct automatic turning of the steering wheel by the system and the associated collision avoidance. However, the stopping distance is much longer at a higher speed, so the inertia of the parking assistance system has an even more serious effect and the risk of collisions in the parking direction increases.
Another problem with many parking assistance systems is that under certain conditions the parking limit is not perceived by the parking assistance system. This may be the case in particular when the detection range of the sensors in the parking direction is too small, if the sensors are inactive or if there is some other external disturbance. In such a case, for lack of detection of the parking limit, it is impossible to calculate the distance remaining until collision, so there may not be a collision warning, which greatly increases the risk of a collision because the driver usually relies on such a warning.